1. Field of the Invention
The present invention relates to a wear resistant material having excellent wear resistance and a method of manufacturing the material, and more particularly to a wear resistant material and a method of manufacturing the material, which has excellent wear resistance and has multi-layers including a solid lubricant layer that provides lubrication into bearing inside lace or contact moving side of pin/bush joint where it is difficult to re-fill the lubricant or to stop the contact moving side for oiling as in the case of a food machine, ship or plane.
2. Description of the Prior Art
In general, wear resistance material used in the joint part of a machinery has resistance against friction wear under high-load and low-speed because of hardness improved by surface hardening method such as carburization, induction hardening and nitriding. However, lubrication of the material is so poor that its friction coefficient is high when the corresponding friction material is iron, since a hard compound layer on the material is formed on iron substrate by the carburizing layer, the nitriding layer or the induction hardening layer or hardened by the martensite transformation of simple rapid heating-cooling as described in the U.S. Pat. No. 5,217,544.
In one prior art attempt to solve the above problem, lubricating film has been formed by providing lubricant to the contact moving side. If, however, low viscous lubricant oil is used as the lubricant, the film will break readily so that there will be the metal-metal friction. Also a high performing leak-preventing apparatus is needed to keep constant lubrication. Use of a highly viscous grease oil with respect to said problem results in preservation of the oil film and little oil-leaking. But there are some problems, e.g., the lubricant swept away from the surface during contact moving can not be provided again, and which the grease is decomposed by heating from the friction. In order to apply the high viscous lubricant such as grease, a given pressure under which the lubricant can be refilled into the oil crack of the friction substrate is used. On the friction substrate, groove is formed as a passage for active filling of the lubricant.
To maintain the lubricating effect, the lubricant needs to be filled periodically and many filling places are required due to the short term of filling, leading to time consumption. Also, if the filling place is located high or amidst complicated parts, it will be hard to mend or check the machine. Accordingly, the lubrication conditions should be noticed because, otherwise there will be damage caused by scoring and scuffing friction, and then the damage will grow into seams or result in stoppage of the machine.
To prevent the above problem, a method of applying MoS.sub.2 and PTFE solid lubricant is disclosed in the U.S. Pat. Nos. 5,271,679, 5,332,422, 5,222,816, 5,207,513, and 5.271,619. These solid lubricant coating leads not only to low friction coefficient, but to the decrease of load supporting capability (pressure resistance) of their surface. In particular, under shearing force by friction, the lubricant layer can be removed readily from the surface, and required lubrication and its function can be lost earlier.
In addition, hard chromium coating as disclosed in the U.S. Pat. No. 5,277,785 leads not only to high hardness and high iron affinity, but to scoring friction wear by being peeled during friction due to the fact that the thickness of the coating layer is 20-30 microns. There are additional coating methods for surface hardening, e.g., plasma spraying of hard materials such as alumina dislosed in the U.S. Pat. No. 5,305,726, high melting and hardness chromate oxide disclosed in the U.S. Pat. No. 5,230,750, tungsten carbide disclosed in the U.S. Pat. No. 5,201,917, boron compound disclosed in the U.S. Pat. Nos. 5,194,304, 5,313,919 and 5,332,422, and titanium nitrate disclosed in the U.S. Pat. No. 5,213,848. These materials, however, have low adhesion to steel substrate, and their physical property such as thermal expansion coefficient differs from all. Also their low bending and impact resistance that of the steel substrate limit their use to wear material for mere sliding action.